In recent years, an organic EL element utilizing an organic substance has a bright prospect of application as a low priced full color display element having a large area and a light source alley for writing, as a solid emission type, and active research and development thereof is on the way. An organic EL element is a thin film type element which is provided with the first electrode (a cathode or an anode), an organic compound layer (comprising a single layer or plural layers) containing an organic emission substance being accumulated thereon, that is a light emission layer, and the second electrode (a cathode or an anode) accumulated on said light emission layer. When voltage is applied on such an organic EL element, an electron is injected into an organic compound layer from the cathode and a hole is injected from the anode. It is known that said electron and hole are recombined in an emission layer and light emission is obtained by releasing energy as light at the time of an energy level returns to a valence electron band from a conduction band.
As described above, since an organic EL element is a thin film type element, an apparatus equipped with a panel light source can be easily made to be a thin layer type when an organic EL panel, comprising one or plural number of organic EL elements formed on a substrate, is utilized as a plane light source of such as a backlight. Further, when a display device is constituted utilizing an organic EL element panel, in which a predetermined number of organic EL elements as pixels are formed on a substrate, as a display panel, there are advantages such as high visual recognition and no viewing angle dependence, which are not available with a liquid crystal display.
On the other hand, at the time of forming an organic compound layer of an organic EL element, various methods such as an evaporation method, a sputtering method, a CVD, a PVD, a coating method utilizing a solvent, as described in JP-A Nos. 9-102393 and 2002-170676 (hereinafter, JP-A refers to Japanese Patent Publication Open to Public Inspection No.); however, among these, it is known that a wet film forming method such as a coating method is advantageous in view of such as simplification of a manufacturing process, reduction of a manufacturing cost, improvement of a processing property and an application to a flexible element having a large area such as a backlight and an illumination light source. For example, a method to form an organic compound layer on a glass plate of a sheet form by a spin coat method is described in JP-A 2002-170676. A method to successively form organic compound layers on a glass plate of a sheet form by an inkjet method is described in JP-A 2003-142260. In any of these methods, an apparatus becomes large as well as a cost becomes high to manufacture a full color display element having a large area because a sheet form substrate is utilized as a substrate. Therefore, studies are made on a method to manufacture an organic EL element, which has a bright prospect of application as a low priced full color display element having a large area and a light source alley for writing, as a solid emission type. For example, known is a method in which patterning of one or a plural number of emission layers comprising an organic substance and patterning of a cathode are performed by means of a roll to roll method and an evaporation under vacuum method as a method to manufacture an organic EL display in which plastic film is utilized as a transparent substrate and one or a plural number of emission layers comprising an organic substance and an anode layer are provided on this plastic film (for example, refer to patent literature 1).
Since a roll to roll method described in patent literature 1 enable mass production different from a conventional sheet method, manufacturing of an organic EL element is possible at a low cost, however, there are following disadvantages.
1) The using efficiency of an organic substance, which is utilized to form one or a plural number of emission layers comprising an organic substance is low, which is one reason to increase the cost.
2) Since it is a method to form one or a plural number of emission layers comprising an organic substance by an evaporation method, it is difficult to scale up because an evaporation room has to be made large accordingly to require associated equipment having a high capacity, to prepare a display element having a large area.
3) Since it is a method to form one or a plural number of emission layers comprising an organic substance by an evaporation method, it takes long time to form an emission layer resulting in difficulty to increase productivity.
4) Particularly in the case of an organic EL element utilized for an illumination application, it is difficult to form an organic EL element having a large area without unevenness because an organic EL element having a large area has to be formed in an evaporation method.
In view of these situations, desired has been development of a forming method of an organic compound layer for an organic EL element application having high productivity without increasing a cost and having a large area without unevenness, a manufacturing method of an organic EL element utilizing said organic compound layer and an organic EL element.
[Patent Literature 1] PCT International Application Publication No. 01/5194 Pamphlet